JP7403354B2 - induction heating cooker - Google Patents

Description

The present disclosure relates to an induction heating cooker that supplies high-frequency current to a plurality of heating coils from one inverter.

There is an induction cooking device that includes a plurality of heating coils and an inverter circuit that supplies high-frequency current to the plurality of heating coils. Such an induction heating cooker uses a discontinuous operation in which the current flowing through the heating coil is zero for a certain period of time, and a continuous operation in which the current flowing in the heating coil is not zero. A technique has been proposed for controlling the power input to the device (for example, see Patent Document 1).

Patent No. 6340550 (page 14)

When you want to heat at low output for a long time, such as when making stews, or when you want to keep the heated object warm, the amount of heat required per unit time is higher than when boiling the liquid inside the heated object or frying. It is desirable to reduce the electric power input to the object to be heated. In the induction heating cooker described in Patent Document 1, in discontinuous operation in which the current flowing through the heating coil is zero for a certain period of time, by lengthening the period in which the current is zero, it is possible to The power input per unit time is reduced. However, when discontinuous operation with a period of zero current is used for current control to heat or keep the heated object at low output, when the current flowing through the heating coil is zero, the heated object There was a problem in that the temperature of the device would drop, making it less convenient to use.

In addition, when trying to set the average power input to the heated object per unit time to the desired power, discontinuous operation in which the current flowing through the heating coil is zero, compared to continuous operation, You need to increase the value. As the current flowing through the heating coil increases, the amount of heat generated by the heating coil and the inverter also increases, so it is necessary to increase the ability to cool them. That is, if the average power input to the heated object per unit time is the same in discontinuous operation and continuous operation, the cooling load will be larger in discontinuous operation than in continuous operation. This leads to an increase in the size of the radiation fin when the radiation fin is used as a cooling means for the inverter. Furthermore, when a blower is used as a cooling means for the heating coil and the inverter, the blower becomes larger, generates more noise, or increases power consumption.

The present disclosure is related to the above-mentioned problem, and it is possible to gradually reduce the power input to a heated object from a plurality of heating coils connected to one inverter without reducing the current flowing through the heating coils to zero. To obtain an induction heating cooker that can be controlled precisely.

The induction cooking device according to the present disclosure includes an inverter having at least two main switching elements connected in series, a first heating coil, and a first resonant capacitor connected in series with the first heating coil, a first resonant circuit connected between the output of the inverter and a power supply line or a GND line; a second heating coil; and a second resonant capacitor connected in series with the second heating coil; a second resonant circuit connected between the output and the GND line, a sub switch and a sub capacitor connected in series with the sub switch, and in parallel with the second resonant capacitor of the second resonant circuit. and a connected sub-circuit , the inverter outputs a high frequency current having a frequency higher than the resonance frequency of the first heating coil and the second heating coil, and simultaneously outputs a high frequency current to the first heating coil and the second heating coil. When applying power and increasing the input current to the heated object placed on the first heating coil, the inverter changes the frequency of the high-frequency current from the first frequency to The frequency is changed to a second frequency smaller than the first frequency, and the sub switch is switched from an off state to an on state .

According to the technology of the present disclosure, by switching the sub-switch of the sub-circuit between the on state and the off state, the current flowing through the heating coils is not reduced to zero, and the electrical current from a plurality of heating coils connected to one inverter is removed. The power input to the heated object can be controlled in stages.

FIG. 1 is an exploded perspective view of the induction heating cooker 100 according to the first embodiment. 1 is a diagram showing a circuit configuration of an induction heating cooker 100 according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating a high frequency current flowing through the first heating coil 11 according to the first embodiment. FIG. 3 is a diagram illustrating high frequency current flowing through the second heating coil 13 according to the first embodiment. 5 is a diagram showing resonance characteristics of a first resonant circuit 51 and a second resonant circuit 52 according to the first embodiment. FIG. FIG. 3 is a diagram illustrating changes in power input to the first heating port 3A and the second heating port 3B according to the first embodiment. It is a figure which shows the time change of the input power to the 2nd heating port 3B based on this Embodiment. FIG. 3 is a diagram illustrating a discontinuous operation having a period in which input power is zero. FIG. 2 is a diagram showing a circuit configuration of an induction heating cooker 100 according to a second embodiment. 7 is a diagram illustrating a configuration example of a second heating coil 13 and a sub-coil 153 according to Embodiment 2. FIG. 5 is a diagram showing resonance characteristics of a first resonant circuit 51 and a second resonant circuit 52 according to Embodiment 3. FIG. FIG. 3 is a diagram showing a circuit configuration of an induction heating cooker 100 according to a fourth embodiment. 12 is a flowchart illustrating control when an on operation is applied to the second operation unit 4B according to the fourth embodiment. 12 is a flowchart illustrating control of the induction heating cooker 100 according to Embodiment 5 according to the material of the object to be heated. It is a figure explaining the circuit structure of induction heating cooker 100 concerning Embodiment 6. It is a figure explaining the circuit structure of induction heating cooker 100 concerning Embodiment 7. It is a figure explaining the circuit structure of induction heating cooker 100 concerning Embodiment 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which an induction heating cooker according to the present disclosure is applied to an induction heating cooker that is incorporated into a kitchen stand or is used stationary will be described with reference to the drawings. The technology described in this disclosure can be modified in various ways without departing from the spirit. Further, in the following, all combinations of configurations that can be combined among the configurations shown in each embodiment will be disclosed. Furthermore, in each figure, the same reference numerals are the same or equivalent, and this is common throughout the entire specification. Note that in each drawing, the relative dimensional relationship or shape of each component may differ from the actual one.

Embodiment 1.
FIG. 1 is an exploded perspective view of an induction heating cooker 100 according to the first embodiment. In FIG. 1, an object to be heated 200 such as a pot heated by the induction heating cooker 100 is also illustrated, and a part of the housing 2 is shown cut away for explanation. The induction heating cooker 100 includes a top plate 1 on which an object to be heated 200 is placed, and a generally box-shaped housing 2 provided under the top plate 1. At the top of the induction heating cooker 100, an operation section 4 that receives operation input and a display section 5 that displays information are provided. A first heating coil 11 and a second heating coil 13 are provided under the top plate 1 for induction heating an object to be heated 200 placed on the top plate 1. A control device 6 and an inverter 20 are housed within the housing 2.

The top plate 1 is made of a non-metallic material such as heat-resistant glass or ceramic. The top plate 1 is provided with a first heating port 3A and a second heating port 3B, which are areas on which the object to be heated 200 is placed. On the top plate 1 of this embodiment, the outer edges of the first heating port 3A and the second heating port 3B are shown by printing. Although FIG. 1 shows an example in which circular first heating ports 3A and second heating ports 3B are provided, the shape and number of the first heating ports 3A and second heating ports 3B are limited to the illustrated example. Not done.

The first heating coil 11 is placed under the first heating port 3A, and the second heating coil 13 is placed under the second heating port 3B. The first heating coil 11 and the second heating coil 13 are coils formed by winding a conducting wire such as a copper wire or an aluminum wire, and generate a high-frequency magnetic field when a high-frequency current is supplied thereto.

The control device 6 controls the energization of the first heating coil 11 and the second heating coil 13 by controlling the inverter 20 . The control device 6 controls the inverter so that desired electric power is supplied to the objects to be heated placed in the first heating port 3A and the second heating port 3B based on the information input through the operation unit 4. Control 20. In the following description, the power input to the object to be heated placed in the first heating port 3A may be referred to as the power input to the first heating port 3A. Further, the power input to the object to be heated placed in the second heating port 3B may be referred to as the power input to the second heating port 3B. The control device 6 is composed of hardware such as a circuit device that realizes its functions, or an arithmetic device such as a microcomputer, and software executed thereon.

FIG. 2 is a diagram showing a circuit configuration of the induction heating cooker 100 according to the first embodiment. In FIG. 2, a commercial AC power source 40 that supplies power to the induction heating cooker 100 is also illustrated. The induction heating cooker 100 includes a direct current conversion means 41, an inverter 20 connected to the output side of the direct current conversion means 41, a power supply line 42 that supplies a power supply potential, and a GND line 43 that supplies a reference potential. The DC converting means 41 includes a diode bridge and converts AC power supplied from the commercial AC power supply 40 into DC power.

The inverter 20 converts the DC power output from the DC conversion means 41 into high frequency power, and supplies this high frequency power to the first heating coil 11 and the second heating coil 13. The inverter 20 is a half-bridge inverter having a first main switching element 21 and a second main switching element 22. The first main switching element 21 and the second main switching element 22 are connected in series between the power supply line 42 and the GND line 43. An output point of the inverter 20 is located between the first main switching element 21 and the second main switching element 22. A gate terminal of the first main switching element 21 and a gate terminal of the second main switching element 22 are connected to the control device 6.

The first main switching element 21 and the second main switching element 22 are made of, for example, a wide bandgap semiconductor. Wide bandgap semiconductor is a general term for semiconductor elements that have a larger bandgap than silicon. Wide band gap semiconductors include silicon carbide, gallium nitride based materials, diamond or gallium nitride. By configuring the first main switching element 21 and the second main switching element 22 from wide bandgap semiconductors, it is possible to reduce the conduction loss of the switching elements. Furthermore, since wide bandgap semiconductors have good heat dissipation properties, it is possible to make the heat dissipation fins smaller even when the switching frequency when driving the first main switching element 21 and the second main switching element 22 is set to a high frequency. can. Therefore, it is possible to reduce the size and cost of the cooling structure for the inverter 20. In addition, since wide bandgap semiconductors do not easily deteriorate in performance even under high temperatures, the first main switching element 21 and the first main switching element 21 and The reliability of the two main switching elements 22 can be maintained.

A first heating coil 11 and a first resonant capacitor 12 are connected in series between the output point of the inverter 20 and the power supply line 42 . The first heating coil 11 and the first resonant capacitor 12 form a first resonant circuit 51 .

A second heating coil 13 and a second resonant capacitor 14 are connected in series between the output point of the inverter 20 and the GND line 43. The second heating coil 13 and the second resonant capacitor 14 form a second resonant circuit 52 .

A subcircuit 15 is connected between the second heating coil 13 and the GND line 43 in parallel with the second resonant capacitor 14 . The sub circuit 15 includes a sub switch 151 and a sub capacitor 152. The sub switch 151 and the sub capacitor 152 are connected in series. The on state and off state of the sub switch 151 are switched by the control device 6. By switching the sub switch 151 between the on state and the off state, the sub capacitor 152 is switched between a connected state and an unconnected state to the second resonant circuit 52. The sub-switch 151 shown in FIG. 2 is composed of a semiconductor element such as an IGBT or a MOSFET, and a gate terminal of the sub-switch 151 is connected to the control device 6. A diode 154 is connected in antiparallel to the sub switch 151 made of a semiconductor element. The sub switch 151 may be made of a wide bandgap semiconductor. Since wide bandgap semiconductors do not easily deteriorate in performance even under high temperatures, the reliability of the sub switch 151 can be maintained within the casing 2 where the temperature tends to increase due to exhaust heat from the first heating coil 11, second heating coil 13, etc. . Note that the sub switch 151 may be a mechanical relay.

FIG. 3 is a diagram illustrating the high frequency current flowing through the first heating coil 11 according to the first embodiment. In FIG. 3, the high-frequency current supplied to the first heating coil 11 among the first heating coil 11 and the second heating coil 13 connected to one inverter 20 is conceptually shown by an arrow. Further, in FIG. 3, illustration of the diode 154 shown in FIG. 2 is omitted to avoid complication of the drawing. In FIG. 3, (a) shows a state where the first main switching element 21 is on and the second main switching element 22 is off, and (b) shows a state where the first main switching element 21 is off and the second main switching element 22 is off. Indicates the on state. A high frequency current is supplied to the first heating coil 11 by alternately switching between the state shown in FIG. 3A and the state shown in FIG. 3B. As shown in FIG. 3A, when the first main switching element 21 is turned on, current flows to the first resonant capacitor 12 via the first heating coil 11. Next, as shown in FIG. 3B, when the first main switching element 21 is turned off and the second main switching element 22 is turned on, the first resonant capacitor 12 is discharged via the first heating coil 11. By repeating the operations in FIG. 3A and FIG. 3B, a high-frequency magnetic field is generated in the first heating coil 11. When this high-frequency magnetic field intersects with an object to be heated, such as a pot, an eddy current is generated in the object to be heated, and the object to be heated generates heat.

FIG. 4 is a diagram illustrating the high frequency current flowing through the second heating coil 13 according to the first embodiment. In FIG. 4, the high-frequency current supplied to the second heating coil 13 of the first heating coil 11 and the second heating coil 13 connected to one inverter 20 is conceptually indicated by an arrow. Further, in FIG. 4, illustration of the diode 154 shown in FIG. 2 is omitted to avoid complication of the drawing. In FIG. 4, (a) shows a state where the first main switching element 21 is on and the second main switching element 22 is off, and (b) shows a state where the first main switching element 21 is off and the second main switching element 22 is off. Indicates the on state. A high frequency current is supplied to the second heating coil 13 by alternately switching between the state shown in FIG. 4 (a) and the state shown in FIG. 4 (b). As shown in FIG. 4A, when the first main switching element 21 is turned on, current flows to the second resonant capacitor 14 via the second heating coil 13. Next, as shown in FIG. 4B, when the first main switching element 21 is turned off and the second main switching element 22 is turned on, the second resonant capacitor 14 is discharged via the second heating coil 13. By repeating the operations in (a) and (b) in FIG. 4, a high frequency magnetic field is generated in the second heating coil 13. When this high-frequency magnetic field intersects with an object to be heated, such as a pot, an eddy current is generated in the object to be heated, and the object to be heated generates heat.

In FIG. 3, the current flow was explained focusing on the first heating coil 11, and in FIG. 4, the current flow was explained focusing on the second heating coil 13. However, the high frequency current output from the inverter 20 is The current flows through both the first heating coil 11 and the second heating coil 13 at the same time. That is, the current flows shown in FIG. 3(a) and FIG. 4(a) occur simultaneously, and the current flows shown in FIG. 3(b) and FIG. 4(b) occur simultaneously. The phase of the current flowing through the first heating coil 11 and the second heating coil 13 in FIGS. 3(a) and 4(a) is different from that in the first heating coil 11 and the second heating coil 13 in FIG. This is the opposite phase of the current flowing through the heating coil 13.

Furthermore, in FIG. 4, the current flowing through the sub circuit 15 when the sub switch 151 is in the on state is conceptually indicated by a broken line arrow. As shown in FIG. 4A, when the first main switching element 21 is turned on, current flows to the sub capacitor 152 via the second heating coil 13. Since the sub capacitor 152 and the second resonant capacitor 14 are connected in parallel, when the sub switch 151 is in the on state, the second heating coil 13, the second resonant capacitor 14, and the sub capacitor 152 form a resonant circuit. Ru. Next, as shown in FIG. 4B, when the first main switching element 21 is turned off and the second main switching element 22 is turned on, the sub capacitor 152 is discharged via the second heating coil 13.

The frequency at which the first main switching element 21 and the second main switching element 22 are switched between the on state and the off state, that is, the frequency of the high frequency current output from the inverter 20 is referred to as a drive frequency. The control device 6 shown in FIG. 2 controls the power input to the object to be heated by the first heating coil 11 and the second heating coil 13 by controlling the drive frequency.

FIG. 5 is a diagram showing resonance characteristics of the first resonant circuit 51 and the second resonant circuit 52 according to the first embodiment. In FIG. 5, the horizontal axis shows the driving frequency of the inverter 20, and the vertical axis shows the admittance (1/Ω). In FIG. 5, the resonance characteristics of the first resonant circuit 51 shown in FIG. 2 are shown by a characteristic 61, and the resonance characteristics of the second resonant circuit 52 shown in FIG. 2 are shown by characteristics 62 and 62A. The frequency at the peak of the resonance characteristic indicates the resonance frequency. In FIG. 5, the resonant frequency of characteristic 61 is indicated by f0_1, the resonant frequency of characteristic 62 is indicated by f0_2, and the resonant frequency of characteristic 62A is indicated by f0_2A. Here, the resonant frequency f0 of the resonant circuit is expressed as f0=1/2π√(L value×C value). The L value is the self-inductance value of the coil of the resonant circuit, and the C value is the capacitance value of the capacitor.

The driving frequency of the first main switching element 21 and the second main switching element 22 is set in the range of 20 kHz to 100 kHz by regulations of the Radio Law. In the half-bridge type inverter 20 shown in FIG. 2, the driving frequency is changed within this range when controlling the electric power input to the heated object. Specifically, as shown in characteristic 61 in FIG. 5, when the drive frequency is lowered from the first frequency f1 to the second frequency f2, the drive frequency approaches the resonant frequency of the first resonant circuit 51. This makes it easier to apply electric power to the object to be heated placed on the first heating coil 11. This is because as the driving frequency approaches the resonant frequency, the admittance increases, that is, the impedance decreases. The driving frequency is controlled in a frequency range higher than the resonant frequencies of the first resonant circuit 51 and the second resonant circuit 52. In the example of FIG. 5, the resonant frequency f0_1 of the first resonant circuit 51 is higher than the resonant frequency f0_2 of the second resonant circuit 52, so in this embodiment, the drive frequency is controlled in a frequency range higher than f0_1. be done. In this way, by changing the drive frequency of the inverter 20, control of the power input to the object to be heated is realized.

In FIG. 5, a characteristic 62 indicates a state in which the sub switch 151 is off, and a characteristic 62A indicates a state in which the sub switch 151 is on. When the sub switch 151 is off, the resonant frequency of the second resonant circuit 52 is f0_2=1/2π√(L2×C2). Here, L2 is the self-inductance value of the second heating coil 13, and C2 is the capacitance value of the second resonant capacitor 14. When the sub switch 151 is on, the second resonant capacitor 14 and the sub capacitor 152 are connected in parallel, so that the combined capacitance value becomes C2+C3. Here, C3 is the capacitance value of the sub-capacitor 152. Then, the resonant frequency f0_2A when the sub switch 151 is on is expressed as f0_2A=1/2π√(L2×(C2+C3)). That is, the resonant frequency f0_2A when the sub switch 151 is on is smaller than the resonant frequency f0_2 when the sub switch 151 is off.

Therefore, by switching the sub switch 151 between the on state and the off state, the second resonant circuit 52 can obtain two types of resonance characteristics, the characteristic 62 and the characteristic 62A.

In this embodiment, two coils, the first heating coil 11 and the second heating coil 13, are connected to one inverter 20. Here, consider separately controlling the power input to the first heating port 3A corresponding to the first heating coil 11 and the power input to the second heating port 3B corresponding to the second heating coil 13. As described above, when the drive frequency of the inverter 20 is lowered from f1 to f2 in order to increase the power input to the first heating port 3A, the admittance increases from point A to point C of the characteristic 61. Accordingly, the admittance of the characteristic 62 of the second resonant circuit 52 increases from point B to point D. That is, when attempting to increase the power input to the first heating port 3A, the power input to the second heating port 3B also increases at the same time.

Therefore, when lowering the drive frequency from the first frequency f1 to the second frequency f2, the sub switch 151 of the sub circuit 15 is turned on. Then, the resonance characteristic of the second resonant circuit 52 becomes a state shown by a characteristic 62A. The admittance D1 in the characteristic 62A when the driving frequency is the second frequency f2 is the same as the admittance B in the characteristic 62 when the driving frequency is the first frequency f1. Therefore, even if the drive frequency decreases from the first frequency f1 to the second frequency f2, the power input to the second heating port 3B does not change. In this way, the output from one inverter 20 can independently control the power input to the first heating port 3A and the power input to the second heating port 3B.

FIG. 6 is a diagram illustrating changes in the power input to the first heating port 3A and the second heating port 3B according to the first embodiment. FIG. 6A shows changes in the power input to the first heating port 3A and the second heating port 3B when the drive frequency is changed with the sub switch 151 in the off state. As shown in FIG. 6A, when the drive frequency of the inverter 20 is lowered from the first frequency f1 to the second frequency f2, the power input to the first heating port 3A increases from 500W to 2500W. In the example of FIG. 6A, since the drive frequency is swept from the first frequency f1 to the second frequency f2, the power input to the first heating port 3A also changes continuously from 500W to 2500W. As also explained in FIG. 5, as the drive frequency decreases, the power input to the second heating port 3B increases from 200W to 1000W.

FIG. 6(b) shows a change in input power when the sub switch 151 of the sub circuit 15 is switched in accordance with a change in the drive frequency. As shown in FIG. 6B, when the sub switch 151 is off, 500 W is applied to the first heating port 3A and 200 W is applied to the second heating port 3B. As shown in FIG. 6(a), when the drive frequency of the inverter 20 is lowered from the first frequency f1 to the second frequency f2, the power input to the first heating port 3A increases from 500W to 2500W. be. Along with this, the power input to the second heating port 3B increases from 200 W to 1000 W, and at this time, the sub switch 151 is turned on. Then, the power input to the second heating port 3B becomes 200W again. In this way, by lowering the drive frequency and switching the sub switch 151 from off to on, the drive frequency of the power input to the second heating port 3B is changed while increasing the power input to the first heating port 3A. It can be maintained in the previous state. That is, the power input to the first heating port 3A and the power input to the second heating port 3B can be individually controlled.

Note that when the sub switch 151 is turned on using an IGBT as the sub switch 151, the gate voltage applied to the sub switch 151 may be gradually increased. In this way, the power input to the second heating port 3B gradually decreases from 1000W to 200W. By gradually lowering the input power, it is possible to suppress abnormal noises generated from an object to be heated, such as a pot, when the power changes suddenly.

FIG. 7 is a diagram showing a temporal change in the power input to the second heating port 3B according to the present embodiment. FIG. 7 shows changes in the power input to the second heating port 3B by switching the sub switch 151 of the sub circuit 15 between the on state and the off state. Assuming that the drive frequency is constant, the power input to the second heating port 3B differs depending on when the sub switch 151 is off and on. As shown in FIG. 5, if the drive frequency is the second frequency f2, the admittance represented by point D of the characteristic 62 when the sub switch 151 is off and the admittance when the sub switch 151 is on This is due to the fact that the admittance represented by the point D1 of the characteristic 62A differs depending on the state. Therefore, by turning off the sub switch 151, input power P1 shown in FIG. 7 is obtained, and by turning on sub switch 151, input power P2 shown in FIG. 7 is obtained. Note that input power P1 is larger than input power P2.

Since a high frequency current flows through the second heating coil 13 both when the sub switch 151 is on and off, the power input to the second heating port 3B does not become zero. That is, input power P1 and P2 are values larger than zero. In this way, by switching the sub switch 151 between the on state and the off state and adjusting the ratio of the time between the on state and the off state, it is possible to reduce the power input to the second heating port 3B by unit without reducing it to zero. Power input per hour can be controlled to a desired value. The control for alternately inputting input power P1 and input power P2 to the second heating port 3B as shown in FIG. It is suitable for heating for a long time, and the usability of the induction heating cooker 100 can be improved.

FIG. 8 is a diagram illustrating discontinuous operation having a period in which input power is zero. In FIG. 8, input power P4 is zero. As shown in FIG. 8, when the state of input power P3 and the state of input power P4 are alternately repeated, the input power per unit time can be controlled to a desired value. However, since there is a state in which the input power is zero, if an attempt is made to keep the heated object warm through this discontinuous operation, the temperature of the heated object will drop during the period when the input power is zero. Furthermore, if the input power per unit time is to be the same value as the present embodiment shown in FIG. 7, the input power P3 needs to be larger than the input power P1. That is, if a period in which input power is zero is provided as shown in FIG. 8, the maximum value of input power must be increased. When the input power increases, the amount of heat generated by the heating coil and the inverter increases, and it becomes necessary to increase the cooling capacity of the heating coil and the inverter.

However, according to the present embodiment shown in FIG. 7, input power P1 can be made smaller than input power P3 in FIG. can do. Furthermore, according to the present embodiment, since the amount of variation between input power P1 and input power P2 is smaller than the amount of variation between input power P3 and input power P4, temperature changes of the heated object can be prevented. Hard to cause. Therefore, according to the present embodiment, it is possible to control input power suitable for keeping the heated object warm.

As described above, the induction heating cooker 100 of this embodiment includes the inverter 20 having the first main switching element 21 and the second main switching element 22 connected in series. A first resonant circuit 51 is connected between the output of the inverter 20 and the power line 42. The first resonant circuit 51 includes a first heating coil 11 and a first resonant capacitor 12 connected in series with the first heating coil 11 . Further, a second resonant circuit 52 is connected between the output of the inverter 20 and the GND line 43. The second resonant circuit 52 includes a second heating coil 13 and a second resonant capacitor 14 connected in series with the second heating coil 13 . Further, a sub-circuit 15 is connected in parallel with the second resonant capacitor 14 of the second resonant circuit 52 . The sub circuit 15 includes a sub switch 151 and a sub capacitor 152 connected in series with the sub switch 151. Therefore, by switching the sub switch 151 on and off, the first heating coil 11 and the second heating coil 13 connected to one inverter 20 can be connected to one inverter 20 without reducing the current flowing through the second heating coil 13 to zero. The power input from each to the heated object can be controlled in stages.

Embodiment 2.
This embodiment includes a subcircuit 15A having a different configuration from the subcircuit 15 of the first embodiment. In this embodiment, differences from Embodiment 1 will be mainly described.

FIG. 9 is a diagram showing a circuit configuration of an induction heating cooker 100 according to the second embodiment. In FIG. 9, the mutual positions of the first heating coil 11 and the first resonant capacitor 12 are opposite to those shown in FIG. 2. Further, in FIG. 9, the positions of the second heating coil 13 and the second resonant capacitor 14 are opposite to those shown in FIG. 2.

The sub circuit 15A of this embodiment includes a sub switch 151 and a sub coil 153. The sub switch 151 and the sub coil 153 are connected in series. The subcircuit 15A is connected in parallel with the second heating coil 13 between the second resonant capacitor 14 and the GND line 43. By switching the sub switch 151 between the on state and the off state, the sub coil 153 is switched between a connected state and an unconnected state to the second resonant circuit 52.

FIG. 10 is a diagram illustrating a configuration example of the second heating coil 13 and the sub coil 153 according to the second embodiment. The second heating coil 13 and the sub coil 153 are provided at a position facing the second heating port 3B shown in FIG. 1, and function as a heating source for the object to be heated placed in the second heating port 3B. As shown in FIG. 10, the second heating coil 13 and the sub-coil 153 may both be formed in a spiral shape and arranged in parallel. In addition, an annular auxiliary coil 153 may be arranged on the inner peripheral side of the annular second heating coil 13. The sub coil 153 is connected to the second heating coil 13 via the sub switch 151.

When the sub switch 151 is in the on state, the second heating coil 13 and the sub coil 153 function as a heating source for the second heating port 3B, and when the sub switch 151 is in the off state, only the second heating coil 13 functions as the second heating source. It functions as a heating source for the mouth 3B.

In this embodiment, the power input to the second heating port 3B is controlled similarly to the first embodiment by switching the sub switch 151 of the sub circuit 15A between the on state and the off state. This will be explained in detail below.

It has been explained that the resonant frequency f0 of the resonant circuit is expressed as resonant frequency f0=1/2π√(L value×C value). This is applied to the resonant frequency f0_2 of the second resonant circuit 52 of this embodiment. When the sub switch 151 is in the off state, the resonance frequency f0_2=1/2π√(L2×C2). Here, L2 is the self-inductance value of the second heating coil 13, and C2 is the capacitance value of the second resonant capacitor 14. When the sub switch 151 is in the on state, the resonance frequency f0_2=1/2π√(L2//L3×C2). L3 is the inductance value of the sub coil 153, and L2//L3=L2×L3/(L2+L3).

In this embodiment, the number of turns of the coil of the second resonant circuit 52 is switched by switching the sub switch 151 between the on state and the off state. When the sub switch 151 is turned off, the L value becomes larger than when the sub switch 151 is turned on, so the resonant frequency f0_2 becomes smaller. That is, referring to FIG. 5, when the sub switch 151 is in the off state, characteristic 62A is obtained, and when the sub switch 151 is in the on state, characteristic 62 is obtained. Therefore, in FIG. 5, when it is desired to reduce the drive frequency from the first frequency f1 to the second frequency f2, increase the power input to the first heating port 3A, and maintain the power input to the second heating port 3B without increasing it. Then, the sub switch 151 is switched from on to off. By doing so, the power input to the first heating port 3A and the power input to the second heating port 3B can be controlled in a stepwise manner.

As described above, this embodiment includes the inverter 20 having the first main switching element 21 and the second main switching element 22 connected in series. A first resonant circuit 51 is connected between the output of the inverter 20 and the power line 42. The first resonant circuit 51 includes a first heating coil 11 and a first resonant capacitor 12 connected in series with the first heating coil 11 . Further, a second resonant circuit 52 is connected between the output of the inverter 20 and the GND line 43. The second resonant circuit 52 includes a second heating coil 13 and a second resonant capacitor 14 connected in series with the second heating coil 13 . Further, a subcircuit 15A is connected in parallel to the second heating coil 13 of the second resonant circuit 52. The sub circuit 15A includes a sub switch 151 and a sub coil 153 connected in series with the sub switch 151. Therefore, by switching the sub switch 151 on and off, the first heating coil 11 and the second heating coil 13 connected to one inverter 20 can be connected to one inverter 20 without reducing the current flowing through the second heating coil 13 to zero. The power input from each to the heated object can be controlled in stages.

Moreover, in this embodiment, the second heating coil 13 and the sub-coil 153 are arranged as a heating source for one second heating port 3B. In the first embodiment, the sub capacitor 152 was provided in order to obtain the characteristic 62 and the characteristic 62A regarding the resonant frequency of the second resonant circuit 52, but in the present embodiment, similar two types of resonant frequency characteristics are provided. The sub coil 153 for obtaining the temperature is provided as a heating source for the second heating port 3B. That is, in this embodiment, there is no need to add any component for switching the resonance characteristics to the circuit board. Therefore, it is possible to realize miniaturization of the circuit board.

Embodiment 3.
In this embodiment, a means for more finely controlling the power input to the object to be heated will be described. This embodiment will be described assuming that the circuit configuration is the same as that of the first embodiment shown in FIG. Note that the matters described in this embodiment can also be combined with the circuit configuration of Embodiment 2.

FIG. 11 is a diagram showing the resonance characteristics of the first resonant circuit 51 and the second resonant circuit 52 according to the third embodiment. In FIG. 11, a characteristic 62B is shown instead of the characteristic 62A in FIG. The characteristic 62B is a resonance characteristic when the sub switch 151 is in the on state, but the resonance frequency f0_2B of the characteristic 62B is lower than the resonance frequency f0_2A of the characteristic 62A in FIG. In FIG. 5, the admittance (point B) in the characteristic 62 at the first frequency f1 and the admittance (point D1) in the characteristic 62A at the second frequency f2 were the same value. However, in FIG. 11, the admittance at the second frequency f2 (point D2) is a smaller value than the admittance at the characteristic 62 (point B) and the admittance at the characteristic 62A (point D1). That is, when comparing FIG. 11 with FIG. 5, the power input to the second heating port 3B at the second frequency f2 is smaller in the characteristic 62B than in the characteristic 62A.

In FIG. 11, assume that at the second frequency f2, the power input to the second heating port 3B at point D is 1000W, and the power input to the second heating port 3B at point D2 is 100W. By switching the sub switch 151 between the on state and the off state, the power applied to the second heating port 3B is switched between 1000W and 100W. When the power input to the second heating port 3B is set to a value between 1000 W and 100 W, the ratio between the on time and the off time of the sub switch 151 is changed. For example, if you want to obtain the power (=200W) at point D1 in FIG. get. Then, the sub switch 151 is switched between the on state and the off state so that the on time of the sub switch 151 becomes d (=88.9%). In this way, by adjusting the on/off time ratio of the sub switch 151, a desired input power can be obtained as an average value of input power per unit time.

Note that in order to change the characteristic 62A shown in FIG. 5 to the characteristic 62B shown in FIG. 11, the capacitance value of the sub-capacitor 152 may be increased. Furthermore, if the sub circuit 15A includes the sub coil 153 as in the second embodiment, the inductance value of the sub coil 153 should be increased to change the characteristic 62A shown in FIG. 5 to the characteristic 62B shown in FIG. do it.

As described above, in this embodiment, when the sub switch 151 is switched between the on state and the off state, two types of resonance characteristics, the characteristic 62 and the characteristic 62B, are obtained in the second resonance circuit 52. Then, the power input to the second heating port 3B at the second frequency f2 in characteristic 62B is smaller than the power input to the second heating port 3B at the first frequency f1 in characteristic 62. , the resonance characteristics of the second resonance circuit 52 were set. By controlling the on/off time ratio of the sub switch 151, the power input to the second heating port 3B can be controlled, so more detailed power control can be performed. Therefore, the usability of the induction heating cooker 100 can be improved.

Here, the resonance characteristics in the resonance circuit also change depending on the material and position of the object to be heated, such as a pot. This is because the inductance value of the heating coil changes depending on the material and position of the object to be heated. However, according to the present embodiment, since there is a margin for adjusting the on/off time ratio of the sub switch 151, differences in resonance characteristics due to differences in the material and position of the heated object can be absorbed, and the input power can be accurately adjusted. can be controlled.

Embodiment 4.
In this embodiment, a mode will be described in which only one of the first heating port 3A and the second heating port 3B can be used. Furthermore, in this embodiment, an example is shown in which a sub switch 151B is provided in place of the sub switch 151 shown in Embodiments 1 and 2. Hereinafter, differences from Embodiments 1 to 3 will be mainly explained.

FIG. 12 is a diagram showing a circuit configuration of induction heating cooker 100 according to Embodiment 4. The sub circuit 15B includes a sub capacitor 152 and a sub switch 151B connected in series. The sub switch 151B is a so-called bidirectional IGBT. Specifically, the sub switch 151B has two circuit sets each including a semiconductor switching element 155 made of a semiconductor element and a diode 154 connected antiparallel to the semiconductor switching element 155. The two sets of circuits consisting of the semiconductor switching element 155 and the diode 154 are connected in anti-series to form a bidirectional conduction circuit. Gate terminals of the two semiconductor switching elements 155 are connected to the control device 6. The semiconductor switching element 155 may be made of a wide bandgap semiconductor. Since wide bandgap semiconductors do not easily deteriorate in performance even under high temperatures, the reliability of the semiconductor switching element 155 can be maintained within the casing 2 where the temperature tends to increase due to exhaust heat from the first heating coil 11, second heating coil 13, etc. can.

By making the sub switch 151B a bidirectional IGBT, unnecessary energization in the sub switch 151B is avoided when the first main switching element 21 and the second main switching element 22 are switched between the on state and the off state. can do. Here, a mode in which the sub switch 151 and the diode 154 made of semiconductor elements shown in FIG. 2 are connected in antiparallel will be referred to as a comparison target. In FIG. 2, even if the sub switch 151 is controlled to be off, when the first main switching element 21 is off and the second main switching element 22 is on, the state is the same as when the sub switch 151 is on. obtain. That is, when the second main switching element 22 is turned on, current flows through the second heating coil 13 in the same direction as the direction from the emitter to the collector of the sub switch 151 (see FIGS. 2 and 4). In this case, a current flows through the diode 154 of the sub switch 151, and the sub switch 151 becomes conductive. That is, when it is desired to turn off the sub switch 151 and disconnect the sub capacitor 152 from the second resonant circuit 52, the sub capacitor 152 ends up being connected to the second resonant circuit 52. If this happens, the accuracy of controlling the power input to the heating port will decrease.

In this embodiment, since the sub switch 151B is configured with a bidirectional IGBT, the sub switch 151B is configured as intended regardless of the on state or off state of the first main switching element 21 and the second main switching element 22. Therefore, it is possible to avoid a conductive state. Therefore, the accuracy of controlling the power input to the heating port can be further improved.

Further, the induction heating cooker 100 is provided with a first operating section 4A and a second operating section 4B, as shown in FIG. The first operation section 4A and the second operation section 4B are input devices such as buttons or switches that accept operation inputs from the user. When an operation is applied to the first operation section 4A and the second operation section 4B, a signal corresponding to the operation is input to the control device 6. The first operation unit 4A is for switching whether or not to use the first heating port 3A corresponding to the first heating coil 11. The second operation part 4B is for switching whether or not to use the second heating port 3B corresponding to the second heating coil 13.

A first switch 31 is provided on the power supply line 42 between the inverter 20 and the first resonant circuit 51. When the first switch 31 is turned off, the first resonant circuit 51 is disconnected from the power supply line 42 . A second switch 32 is provided on the GND line 43 between the inverter 20 and the second resonant circuit 52. When the second switch 32 is turned off, the second resonant circuit 52 is disconnected from the GND line 43.

The control device 6 switches the first switch 31 and the second switch 32 between an on state and an off state based on inputs from the first operating section 4A and the second operating section 4B.

In the induction heating cooker 100 of this embodiment, it is possible to individually set whether to use the first heating port 3A and whether to use the second heating port 3B. Here, the first switch 31 is in an off state when the first heating port 3A is not used, and the second switch 32 is in an off state when the second heating port 3B is not used.

If the user wishes to use only the first heating port 3A, the user performs an on operation on the first operating portion 4A. Then, an on signal indicating that an on operation has been applied to the first operation section 4A is input to the control device 6. The control device 6 switches the first switch 31 from the off state to the on state when an on signal is input from the first operation unit 4A. By doing so, the first resonant circuit 51 is electrically connected to the inverter 20 and becomes in a state where high frequency current can be supplied to the first heating coil 11. Moreover, when the user wants to use only the second heating port 3B, the user performs an on operation on the second operation part 4B. Then, an on signal indicating that an on operation has been applied to the second operation section 4B is input to the control device 6. The control device 6 switches the second switch 32 from the off state to the on state when the on signal is input from the second operation section 4B. By doing so, the second resonant circuit 52 is electrically connected to the inverter 20, and becomes in a state where high frequency current can be supplied to the second heating coil 13.

When only one of the first heating port 3A and the second heating port 3B is used, the high frequency current is supplied only to the first heating coil 11 or the second heating coil 13 corresponding to the one used.

Further, when the user wants to stop using the first heating port 3A while only the first heating port 3A is being used, the user performs an off operation on the first operating portion 4A. Then, an off signal indicating that an off operation has been applied to the first operation section 4A is input to the control device 6. When the off signal is input from the first operation unit 4A, the control device 6 switches the first switch 31 from the on state to the off state. By doing so, the first resonant circuit 51 is electrically disconnected from the inverter 20, and the first heating coil 11 is not supplied with high frequency current. Further, when the user wants to stop using the second heating port 3B while only the second heating port 3B is being used, the user performs an off operation on the second operating portion 4B. Then, an off signal indicating that an off operation has been applied to the second operation section 4B is input to the control device 6. When the off signal is input from the second operation unit 4B, the control device 6 switches the second switch 32 from the on state to the off state. By doing so, the second resonant circuit 52 is electrically disconnected from the inverter 20, and the second heating coil 13 is not supplied with high frequency current.

Next, a case where both the first heating port 3A and the second heating port 3B are used simultaneously will be described. In this embodiment, as shown in FIG. 12, the first resonant circuit 51 and the second resonant circuit 52 are connected to the power supply line 42. When the first switch 31 and the second switch 32 are simultaneously turned on, the power supply voltage is applied to the first resonant capacitor 12 and the second resonant capacitor 14. Further, a sub switch 151B made of a semiconductor element is connected in series to the sub capacitor 152 of the sub circuit 15B. Even if the sub switch 151B is in an off state, a blocking current of μA order flows through the sub switch 151B, which is a semiconductor element. Therefore, when the first switch 31 and the second switch 32 are turned on at the same time, a voltage is applied across the sub-capacitor 152, and the sub-capacitor 152 is also charged. If the sub-switch 151B is turned on with the sub-capacitor 152 charged, there is a risk that an overcurrent will flow through the sub-switch 151B due to the charge in the sub-capacitor 152. In this case, the secondary switch 151B may be damaged by the current exceeding the rated current of the secondary switch 151B. Therefore, the control device 6 of the present embodiment performs the following control when an on operation is applied to the second operating section 4B corresponding to the second resonant circuit 52 to which the subcircuit 15B is connected. .

FIG. 13 is a flowchart illustrating control when an on operation is applied to the second operation unit 4B according to the fourth embodiment. The control device 6 monitors whether an on operation has been applied to the second operation section 4B, that is, whether an on signal has been input from the second operation section 4B (S1). When the second operation unit 4B is turned on (S1; YES), it is checked whether the first switch 31 is in the on state (S2).

When the first switch 31 is in the on state (S2; YES), the sub switch 151B is changed to the on state (S3), and then the second switch 32 is changed to the on state (S4). In this way, if the first switch 31 is already in the on state when the on operation is applied to the second operation section 4B, the second switch 32 is turned on after the sub switch 151B is turned on. By turning on the sub switch 151B in step S3, the charge in the sub capacitor 152 is discharged. By turning on the second switch 32 after the charge in the sub capacitor 152 is discharged, it is possible to avoid a phenomenon in which an overcurrent flows through the sub switch 151B due to the charge in the sub capacitor 152.

When the first switch 31 is not in the on state (S2; NO), the second switch 32 is subsequently changed to the on state (S5). If the first switch 31 is not in the on state, the above-mentioned problems of cutoff current and overcurrent do not occur, so it is not necessary to turn on the second switch 32 after turning on the sub switch 151B.

The control described with reference to FIG. 13 can be applied in the first and third embodiments when the sub switch 151 is a semiconductor element. Note that if the sub switch 151 is a mechanical relay instead of a semiconductor element, the above-mentioned problems of cut-off current and overcurrent do not occur, so the control described in FIG. 13 does not need to be performed. Further, if the resonant circuit is not connected to the power supply line 42 as in the sixth embodiment described later, the sub-capacitor 152 is not charged by the above-mentioned cutoff current, so the control described in FIG. 13 is performed. You don't have to.

Embodiment 5.
Materials for objects to be heated such as pots include magnetic materials such as iron and non-magnetic materials such as aluminum. It is known that the resonant frequency of a resonant circuit differs depending on the material of the heated object. In this embodiment, control of the induction heating cooker 100 according to the material of the object to be heated will be described. Hereinafter, the control of this embodiment will be explained using the induction heating cooker 100 that employs the circuit configuration shown in FIG. 12 as an example.

First, as shown in FIG. 12, the induction heating cooker 100 supplies high frequency current from one inverter 20 to the first heating coil 11 and the second heating coil 13. Therefore, the driving frequency of the high-frequency current supplied to the first heating coil 11 and the driving frequency of the high-frequency current supplied to the second heating coil 13 are naturally the same. When the same type of pot, either a magnetic pot or a non-magnetic pot, is placed in both the first heating port 3A and the second heating port 3B, the resonance frequency in the first heating port 3A and the second heating port 3B The resonant frequencies at approximately coincide with each other. Specifically, referring to FIG. 5, the resonant frequency f0_1 of the characteristic 61 and the resonant frequency f0_2 of the characteristic 62 are in a state in which they almost match. Therefore, when objects to be heated made of the same material are placed in the first heating port 3A and the second heating port 3B, the drive frequency is switched and the energization ratio is controlled as shown in the above embodiment. This makes it possible to input desired electric power to the first heating port 3A and the second heating port 3B.

However, when objects to be heated made of different materials are placed on the first heating port 3A and the second heating port 3B, the resonance frequencies of the first heating port 3A and the second heating port 3B are different. In the heating port on which the non-magnetic pot is placed, the inductance value of the heating coil is small, so the resonant frequency is higher than in the case where the magnetic pot is placed. In FIG. 5, it has been explained that the driving frequency is controlled in a frequency range higher than the resonant frequency, but as the resonant frequency increases, the driving frequency also needs to be increased. For example, the driving frequency of a magnetic pot is about 22 kHz, and the driving frequency of a non-magnetic pot is about 35 kHz. When supplying high-frequency current with the same drive frequency to the two heating ports, if the inverter 20 is controlled according to the drive frequency of the non-magnetic pot, the drive frequency will be too high for the magnetic pot, and the desired power will not be applied to the magnetic pot. Can not. With such matters as a background, control in the case where objects to be heated made of different materials are simultaneously heated by the first heating port 3A and the second heating port 3B will be described below.

FIG. 14 is a flowchart illustrating control of the induction heating cooker 100 according to the fifth embodiment depending on the material of the object to be heated. Here, it is assumed that a magnetic pot which is an object to be heated made of a magnetic material or a non-magnetic pot which is an object to be heated made of a non-magnetic material is placed in the first heating port 3A and the second heating port 3B. Further, it is assumed that the first switch 31 and the second switch 32 shown in FIG. 12 are in the on state.

When an operation to start heating is input to the first heating port 3A and the second heating port 3B, the materials of the objects to be heated in the first heating port 3A and the second heating port 3B are determined (S10). Specifically, the control device 6 controls the inverter 20 to supply a high-frequency current having a frequency for material determination to the first heating coil 11 and the second heating coil 13. The frequency for material determination can be higher than the resonant frequency of the non-magnetic material. By doing so, it is possible to suppress the electric power input to the object to be heated during material determination. While the high-frequency current is being supplied to the first heating coil 11 and the second heating coil 13 at the frequency for material determination, the control device 6 controls the values of the coil current and voltage flowing through the first heating coil 11, and The value of the coil current and the value of the voltage flowing through the second heating coil 13 are detected. The material of the object to be heated can be determined based on the coil current value, voltage value, and phase difference between the coil current and voltage when a specific input current is supplied.

Based on the determination in step S10, if a non-magnetic pot is placed in the first heating port 3A (S11; non-magnetic pot), the sub switch 151B is turned on (S12). Then, the driving frequency is controlled so that the electric power set for the first heating port 3A is preferentially applied to the first heating port 3A (S13).

In this manner, when a heated object made of a non-magnetic material is placed in the first heating port 3A, the sub switch 151B is turned on to increase the resonant capacitor capacity of the second resonant circuit 52. In this state, the drive frequency is controlled so that the electric power set for the first heating port 3A is obtained. Since a heated object made of a non-magnetic material is placed in the first heating port 3A, the driving frequency is controlled to a high value of about 35 kHz. When the capacitor capacity of the second resonant circuit 52 is increased, the resonant frequency of the second resonant circuit 52 decreases, and the electric power that can be input to the second heating port 3B decreases (see characteristic 62A in FIG. 5). However, when the sum of the power input to the first heating port 3A and the second heating port 3B is constant, the power input to the second heating port 3B becomes smaller, and the object to be heated, which is a non-magnetic material with a high resonance frequency, is heated. A large amount of electric power can be input to the mounted first heating port 3A.

In this case, by turning on the sub switch 151B and lowering the resonant frequency of the second resonant circuit 52, the power that can be input to the second heating port 3B becomes smaller, but there is also an advantage. That is, even when the sub switch 151B is turned off, the driving frequency of the inverter 20 increases as the resonance frequency of the first heating port 3A increases, so the power that can be input to the second heating port 3B decreases. . Moreover, since the impedance of the first heating coil 11 on which the non-magnetic pot is placed becomes small, a large output current flows through the first resonant circuit 51. Therefore, the loss of the first main switching element 21 and the second main switching element 22 increases, and as the loss increases, the electric power that can be input to both the first heating port 3A and the second heating port 3B also decreases. Therefore, as in this embodiment, priority is given to heating in the first heating port 3A by turning on the sub switch 151B and suppressing the electric power that can be input to the second heating port 3B. By doing so, although the priority of cooking at the second heating port 3B is lowered, it is possible to improve usability for a user who wants to use a non-magnetic pot at the first heating port 3A.

Based on the determination in step S10, if a magnetic pot is placed on the first heating port 3A (S11; magnetic pot) and a non-magnetic pot is placed on the second heating port 3B, (S14; non-magnetic pot), the use of the second heating port 3B is prohibited (S15).

By disabling non-magnetic pots in the second heating port 3B, desired electric power can be applied to the first heating port 3A on which the magnetic pot is placed. For this reason, it is possible to improve usability for a user who wants to perform cooking using the first heating port 3A. In addition, in this embodiment, when a non-magnetic pot is desired to be used, it can be heated through the first heating port 3A (steps S12 and S13), so that the usability for the user is not significantly impaired.

When prohibiting the use of the second heating port 3B in step S15, it is preferable to display on the display unit 5 that a non-magnetic pot cannot be used in the second heating port 3B. Additionally, information may be displayed to encourage the user to use the first heating port 3A if a non-magnetic pot is desired. Further, in place of or in addition to the display on the display unit 5, the same information may be output by voice. By doing so, it is possible to eliminate user confusion caused by not being able to use the second heating port 3B.

Based on the determination in step S10, if a magnetic pot is placed in the first heating port 3A and the second heating port 3B (S11: magnetic pot, S14: magnetic pot), the set electric power is The driving frequency is controlled so that the heat is supplied to the heating port 3A and the second heating port 3B (S16). The drive frequency control in step S16 is as described in the first embodiment.

As described above, according to the present embodiment, a heated object made of a non-magnetic material can be used in the first heating port 3A. Therefore, the range of selection of objects to be heated such as a pot is expanded, and the user's usability can be improved. While the first heating port 3A is heating a non-magnetic material to be heated, the second heating port 3B can perform heating although the input power is not large. Therefore, the usability of the user who wants to use the two first heating ports 3A and the second heating port 3B at the same time will not be greatly impaired.

Embodiment 6.
In the first to fifth embodiments, examples of circuit configurations have been described in which the first resonant circuit 51 is connected to the power supply line 42 and the second resonant circuit 52 is connected to the GND line 43. In this embodiment, a circuit configuration example in which the first resonant circuit 51 and the second resonant circuit 52 are connected to the GND line 43 will be described. In this embodiment, differences from Embodiments 1 to 5 will be mainly explained.

FIG. 15 is a diagram illustrating a circuit configuration of induction heating cooker 100 according to Embodiment 6. As shown in FIG. 15, a first resonant circuit 51 and a second resonant circuit 52 are connected in parallel between the output of the inverter 20 and the GND line 43. Further, a sub-circuit 15 is connected in parallel with the second resonant capacitor 14 of the second resonant circuit 52 . The first main switching element 21 and the second main switching element 22 are alternately switched from the off state to the on state, thereby supplying high frequency current to the first heating coil 11 and the second heating coil 13. The drive frequency of the inverter 20 and the control of the sub switch 151 of the sub circuit 15 according to the drive frequency are as described in the first embodiment.

As described above, the induction heating cooker 100 of this embodiment includes the inverter 20 having the first main switching element 21 and the second main switching element 22 connected in series. A first resonant circuit 51 is connected between the output of the inverter 20 and the GND line 43. The first resonant circuit 51 includes a first heating coil 11 and a first resonant capacitor 12 connected in series with the first heating coil 11 . Further, a second resonant circuit 52 is connected between the output of the inverter 20 and the GND line 43. The second resonant circuit 52 includes a second heating coil 13 and a second resonant capacitor 14 connected in series with the second heating coil 13 . Further, a sub-circuit 15 is connected in parallel with the second resonant capacitor 14 of the second resonant circuit 52 . The sub circuit 15 includes a sub switch 151 and a sub capacitor 152 connected in series with the sub switch 151. Therefore, by switching the sub switch 151 on and off, the first heating coil 11 and the second heating coil 13 connected to one inverter 20 can be connected to one inverter 20 without reducing the current flowing through the second heating coil 13 to zero. The power input from each to the heated object can be controlled in stages.

Embodiment 7.
In this embodiment, two sub-circuits 15 shown in the first embodiment are provided. Hereinafter, differences from Embodiment 1 will be mainly explained.

FIG. 16 is a diagram illustrating a circuit configuration of induction heating cooker 100 according to Embodiment 7. As shown in FIG. 16, in addition to the sub-circuit 15 provided in the second resonant circuit 52, the sub-circuit 15 is also provided in the first resonant circuit 51. Specifically, a sub-circuit 15 is provided in parallel with the first resonant capacitor 12 . The second embodiment is the same as the first embodiment in that the sub switch 151 and the sub capacitor 152 of the sub circuit 15 are provided in series.

The first main switching element 21 and the second main switching element 22 are alternately switched from the off state to the on state, thereby supplying high frequency current to the first heating coil 11 and the second heating coil 13. Depending on the driving frequency of the inverter 20, the sub switches 151 of the two sub circuits 15 are switched between an on state and an off state.

Here, in FIG. 5, it has been explained that by switching the sub switch 151 provided in the second resonant circuit 52 between the on state and the off state, two types of resonance characteristics, the characteristic 62 and the characteristic 62A, can be obtained. In this embodiment, since the sub-circuit 15 is also provided in the first resonant circuit 51, by switching the sub-switch 151 provided in the sub-circuit 15 between the on state and the off state, the first resonant circuit 51 Also, two types of resonance characteristics can be obtained. That is, two types of resonance characteristics can be obtained in both the first resonance circuit 51 and the second resonance circuit 52. Therefore, by combining the two types of resonance characteristics, it is possible to control the power input to the first heating port 3A and the second heating port 3B in a stepwise manner with higher accuracy.

For example, when power is being applied to both the first heating port 3A and the second heating port 3B, when increasing the power input to the first heating port 3A and maintaining the power input to the second heating port 3B. In this case, the driving frequency of the inverter 20 is lowered. As a result, the drive frequency approaches the resonance frequency of the first heating coil 11, thereby making it possible to increase the power input to the first heating port 3A. At the same time, the sub switch 151 of the sub circuit 15 connected to the second resonant circuit 52 is changed from the off state to the on state. By doing this, the resonant frequency of the second resonant circuit 52 becomes small, so even if the drive frequency decreases, it is possible to avoid an increase in the power input to the second heating port 3B. Note that, as described in the above embodiment, by adjusting the ratio of the on-state time and off-state time of the sub switch 151, more detailed control of the power input to the second heating port 3B is performed. In addition, while power is being applied to both the first heating port 3A and the second heating port 3B, the power input to the first heating port 3A is maintained and the power input to the second heating port 3B is increased. In this case, the driving frequency of the inverter 20 is lowered. As a result, the drive frequency approaches the resonance frequency of the second heating coil 13, thereby making it possible to increase the power input to the second heating port 3B. At the same time, the sub switch 151 of the sub circuit 15 connected to the first resonant circuit 51 is changed from the off state to the on state. By doing so, the resonant frequency of the first resonant circuit 51 becomes small, so even if the drive frequency decreases, it is possible to avoid an increase in the power input to the first heating port 3A. Note that, as described in the above embodiment, by adjusting the ratio between the on-state time and the off-state time of the sub switch 151, more detailed control of the power input to the first heating port 3A is performed.

Embodiment 8.
In this embodiment, two sub-circuits 15A shown in the second embodiment are provided. Hereinafter, differences from Embodiment 2 will be mainly explained.

FIG. 17 is a diagram illustrating a circuit configuration of induction heating cooker 100 according to Embodiment 8. As shown in FIG. 17, in addition to the sub-circuit 15A provided in the second resonant circuit 52, the first resonant circuit 51 is also provided with a sub-circuit 15A. Specifically, a subcircuit 15A is provided in parallel with the first heating coil 11. The second embodiment is the same as the second embodiment in that the sub switch 151 and the sub coil 153 of the sub circuit 15A are provided in series.

The first main switching element 21 and the second main switching element 22 are alternately switched from the off state to the on state, thereby supplying high frequency current to the first heating coil 11 and the second heating coil 13. Depending on the drive frequency of the inverter 20, the on state and off state of the sub switches 151 of each of the two sub circuits 15A are switched.

In this embodiment, the sub-circuit 15A is provided in both the first resonant circuit 51 and the second resonant circuit 52. Therefore, by individually switching the on state and off state of the sub switch 151 provided in each sub circuit 15A, two types of resonance characteristics can be achieved in both the first resonant circuit 51 and the second resonant circuit 52. Obtainable. Therefore, by combining the two types of resonance characteristics, it is possible to control the power input to the first heating port 3A and the second heating port 3B in a stepwise manner with higher accuracy.

For example, when power is being applied to both the first heating port 3A and the second heating port 3B, when increasing the power input to the first heating port 3A and maintaining the power input to the second heating port 3B. In this case, the driving frequency of the inverter 20 is lowered. As a result, the drive frequency approaches the resonance frequency of the first heating coil 11, thereby making it possible to increase the power input to the first heating port 3A. At the same time, the sub switch 151 of the sub circuit 15A connected to the second resonant circuit 52 is changed from the on state to the off state. By doing this, the resonant frequency of the second resonant circuit 52 becomes small, so even if the drive frequency decreases, it is possible to avoid an increase in the power input to the second heating port 3B. Note that, as described in the above embodiment, by adjusting the ratio of the on-state time and off-state time of the sub switch 151, more detailed control of the power input to the second heating port 3B is performed.

Note that the technology disclosed in the above embodiments can also be applied to a rice cooker or an electric pot. In this case, the first heating coil 11 and the second heating coil 13 can induction heat the container of the rice cooker or electric pot. The container of the rice cooker or electric pot that is the object to be heated is unique to the rice cooker or electric pot, so its material is known. Therefore, it is not necessary to perform the control according to the material of the object to be heated as shown in Embodiment 5.

1 Top plate, 2 Housing, 3A first heating port, 3B second heating port, 4 Operation section, 4A First operation section, 4B Second operation section, 5 Display section, 6 Control device, 11 First heating coil, 12 first resonance capacitor, 13 second heating coil, 14 second resonance capacitor, 15 subcircuit, 15A subcircuit, 15B subcircuit, 20 inverter, 21 first main switching element, 22 second main switching element, 31 first Switch, 32 Second switch, 40 Commercial AC power supply, 41 Direct current conversion means, 42 Power line, 43 GND line, 51 First resonant circuit, 52 Second resonant circuit, 61 Characteristics, 62 Characteristics, 62A characteristics, 62B Characteristics, 100 Induction heating cooker, 151 sub switch, 151B sub switch, 152 sub capacitor, 153 sub coil, 154 diode, 155 semiconductor switching element, 200 object to be heated.

Claims (12)

an inverter having at least two main switching elements connected in series;
a first resonant circuit having a first heating coil and a first resonant capacitor connected in series with the first heating coil, and connected between the output of the inverter and a power supply line or a GND line;
a second resonant circuit having a second heating coil and a second resonant capacitor connected in series with the second heating coil, and connected between the output of the inverter and the GND line;
comprising a sub-switch and a sub-capacitor connected in series with the sub-switch, and a sub-circuit connected in parallel with the second resonant capacitor of the second resonant circuit ;
The inverter outputs a high frequency current having a frequency higher than the resonance frequency of the first heating coil and the second heating coil,
When power is simultaneously applied to the first heating coil and the second heating coil, and when the current applied to the object to be heated placed on the first heating coil is increased,
the inverter changes the frequency of the high frequency current from a first frequency to a second frequency smaller than the first frequency,
The secondary switch is switched from an off state to an on state.
Induction heating cooker. The induction according to claim 1 , wherein the ratio of the on-state time and off-state time of the sub-switch per unit time is controlled according to the power required for the second resonant circuit to which the sub-circuit is connected. Heating cooker. a first switch connected in series to the first resonant circuit;
a second switch connected in series to the second resonant circuit;
The sub-switch has two sets of circuits in which diodes are connected in anti-parallel to semiconductor switching elements, and these two sets of circuits are connected in anti-series to form a bidirectional conduction circuit . The induction heating cooker according to claim 2 . a first switch connected in series to the first resonant circuit;
a second switch connected in series to the second resonant circuit;
a first operation section that accepts an operation for switching the first switch between an on state and an off state;
a second operation section that receives an operation for switching the second switch between an on state and an off state;
The first resonant circuit is connected between the output of the inverter and the power supply line,
The sub-switch of the sub-circuit is a semiconductor switching element,
When the first switch is in the on state, if an operation is applied to the second operation unit to turn on the second switch, after turning on the sub switch, The induction heating cooker according to any one of claims 1 to 3 , wherein the second switch is turned on. comprising a control device that determines the material of the heated object placed on the first heating coil and the second heating coil,
When it is determined that the heated object placed on the first heating coil is a non-magnetic material, the second heating coil is turned on by switching the sub switch between an on state and an off state. lower the resonant frequency,
Induction heating according to claim 3 or 4 , wherein when it is determined that the object to be heated placed on the second heating coil is a non-magnetic material, the second switch is turned off. Cooking device. an inverter having at least two main switching elements connected in series;
a first resonant circuit having a first heating coil and a first resonant capacitor connected in series with the first heating coil, and connected between the output of the inverter and a power supply line or a GND line;
a second resonant circuit having a second heating coil and a second resonant capacitor connected in series with the second heating coil, and connected between the output of the inverter and the GND line;
An induction heating cooker comprising: a sub switch; a sub coil connected in series with the sub switch; and a sub circuit connected in parallel with the second heating coil of the second resonant circuit. The inverter outputs a high frequency current having a frequency higher than the resonance frequency of the first heating coil and the second heating coil,
When power is simultaneously applied to the first heating coil and the second heating coil, and when the current applied to the object to be heated placed on the first heating coil is increased,
The frequency of the high frequency current output from the inverter changes from a first frequency to a second frequency smaller than the first frequency,
The induction heating cooker according to claim 6 , wherein the sub switch is switched from an on state to an off state. an inverter having at least two main switching elements connected in series;
a first resonant circuit having a first heating coil and a first resonant capacitor connected in series with the first heating coil, and connected between the output of the inverter and a power supply line or a GND line;
a second resonant circuit having a second heating coil and a second resonant capacitor connected in series with the second heating coil, and connected between the GND line and the output of the inverter;
comprising a sub-switch and a sub-circuit having a sub-capacitor connected in series with the sub-switch,
two said sub-circuits are provided;
One of the sub-circuits is connected in parallel with the first resonant capacitor of the first resonant circuit,
The other of the sub-circuits is connected in parallel with the second resonant capacitor of the second resonant circuit,
The inverter outputs a high frequency current having a frequency higher than the resonance frequency of the first heating coil and the second heating coil,
Increasing the power input to the heated object placed on one of the first heating coil and the second heating coil, and maintaining the input power to the heated object placed on the other. If you do,
The inverter changes the frequency of the high frequency current from a first frequency to a second frequency smaller than the first frequency,
The sub switch of the sub circuit connected to the other of the first heating coil and the second heating coil is switched from an off state to an on state.
Induction heating cooker. an inverter having at least two main switching elements connected in series;
a first resonant circuit having a first heating coil and a first resonant capacitor connected in series with the first heating coil, and connected between the output of the inverter and a power supply line or a GND line;
a second resonant circuit having a second heating coil and a second resonant capacitor connected in series with the second heating coil, and connected between the GND line and the output of the inverter;
comprising a sub switch and a sub circuit having a sub coil connected in series with the sub switch,
two said sub-circuits are provided;
One of the subcircuits is connected in parallel with the first heating coil of the first resonant circuit,
The other one of the subcircuits is connected in parallel to the second heating coil of the second resonant circuit. The inverter outputs a high frequency current having a frequency higher than the resonance frequency of the first heating coil and the second heating coil,
Increasing the power input to the heated object placed on one of the first heating coil and the second heating coil, and maintaining the input power to the heated object placed on the other. If you do,
The frequency of the high frequency current output from the inverter changes from a first frequency to a second frequency smaller than the first frequency,
The induction heating cooker according to claim 9 , wherein the sub switch of the sub circuit connected to the other of the first heating coil and the second heating coil is switched from an on state to an off state. The induction heating cooker according to any one of claims 1 to 10 , wherein the main switching element is made of a wide bandgap semiconductor. The induction heating cooker according to claim 11 , wherein the wide bandgap semiconductor is silicon carbide, gallium nitride-based material, diamond, or gallium nitride.

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